The long term goal of this program is a complete understanding of the capabilities and limitations of auditory information processing in children, the development of auditory processing skills, and how that developmental course may be affected by hearing impairment, deafness, and the use of a cochlear mplant. The current focus of the project is on the strategies used by children to segregate desired auditory signals from interfering sounds. Results to date suggest that most young children display a remarkable nability to perform this segregation in simple detection tasks and in tasks requiring attention to a target speech message in the presence of other speech distracters. The data also reveal large individual differences in source segregation ability, with some teenagers demonstrating child-like performance, and some young school-aged children demonstrating adult-like performance. The adult-child differences are argely consistent with what iresults. The new work also addresses the special selective attention problems faced by children and adults with cochlear implants and evaluates strategies by which selective attention can be enhanced. Auditory selective attention is quantified in four kinds of tasks: 1) simple signal detection, in which the target signal is masked by random multicomponent tonal complexes;2) a speech fundamental frequency discrimination task;3) speech recognition tasks, both with and without a visual representation of the speaker;4) spatial segregation tasks in which the target message and the distracter are spatially separated. The aim of the first task is to quantify auditory selective attention within the constraints of a simple one-parameter model. The second task will produce a scale of talker similarity which will then be used to predict the impact of talker similarity in the selective attention tasks. The third and fourth tasks explore means by which selective attention can be enhanced, eithssessed. The overall importance of this project lies in its study of communication situations common in everyday life. Speech communication in noisy environments is an especially important issue for children who are developing speech and language, and the results of this project will add important new knowledge about how children and adults are able to address this issue.